The clinical significance of hypoxia in human cancers

15N SABRE-SHEATH and NMR/DFT Characterization of Amino-Metronidazole, a Metabolic Product of the Antibiotic and Prospective Hypoxia Contrast Agent Metronidazole

The antibiotic metronidazole (MNZ) has gained interest as a potential MRI contrast agent for imaging hypoxia. 15N-labeled MNZ can be efficiently hyperpolarized via SABRE-SHEATH (Signal Amplification By Reversible Exchange in SHield Enables Alignment Transfer to Heteronuclei), but the envisioned MRI approach requires that MNZ rapidly undergoes structural changes in hypoxic environments with significant 15N frequency differences manifested in its downstream metabolic products. We have performed NMR studies of the anticipated metabolic product amino-MNZ (despite anticipated stability concerns) accompanied by computational density functional theory (DFT) studies to predict the 15N chemical shifts of different relevant species. Direct hyperpolarization of sparse naturally abundant 15N spins in amino-MNZ via SABRE-SHEATH (enhancement up to ∼9400 fold), along with 1H-decoupled 15N NMR, allowed comparison with both 15N3-MNZ and naturally abundant MNZ. The results show significant 15N shift differences that agree with the DFT predictions. Taken together, the results show that it should be possible to readily distinguish the parent MNZ from product amino-MNZ in envisioned MRI approaches at clinically relevant magnetic fields.

Investigating the effects of stereotactic body radiation therapy on pancreatic tumor hypoxia and microvasculature in an orthotopic mouse model using intravital fluorescence microscopy

Despite decades of improvements in cytotoxic therapy, the current standard of care for locally advanced pancreatic cancer (LAPC) provides, on average, only a few months of survival benefit. Stereotactic Body Radiation Therapy (SBRT), a technique that accurately delivers high doses of radiation to tumors in fewer fractions, has emerged as a promising therapy to improve local control of LAPC; however, its effects on the tumor microenvironment and hypoxia remain poorly understood. To explore how SBRT affects pancreatic tumors, we combined an orthotopic mouse model of pancreatic cancer with an intravital microscopy platform to visualize changes to the in vivo tumor microenvironment in real-time. Mice received SBRT (5 × 8 Gy) or were left untreated, and were imaged before and 1, 4, 7, and 14 days after treatment (n = 7/group). A fluorescent human pancreatic cancer cell line (BxPC3-DsRed) engineered to express GFP under hypoxic conditions (driven by hypoxia-inducible factor, HIF) was used to monitor tumor hypoxia. Immunohistochemical staining was also performed on tissues to validate in vivo data. Our findings demonstrate a persistent decrease in pancreatic tumor hypoxia as early as one day after SBRT. This coincided with a decrease in both tumor cell proliferation and cell density in the SBRT group. Reduced demand for oxygen after SBRT (due to cell death and growth arrest from treatment) significantly contributed to reoxygenation of the pancreatic TME. Understanding how this reoxygenation phenomenon occurs in a dose-dependent manner will help improve dosing and fractionation schemes for clinical SBRT.

Myriad factors and pathways influencing tumor radiotherapy resistance

Radiotherapy is a cornerstone in the treatment of various tumors, yet radioresistance often leads to treatment failure and tumor recurrence. Several factors contribute to this resistance, including hypoxia, DNA repair mechanisms, and cancer stem cells. This review explores the diverse elements that drive tumor radiotherapy resistance. Historically, resistance has been attributed to cellular repair and tumor repopulation, but recent research has expanded this understanding. The tumor microenvironment - characterized by hypoxia, immune evasion, and stromal interactions - further complicates treatment. Additionally, molecular mechanisms such as aberrant signaling pathways, epigenetic modifications, and non-B-DNA structures play significant roles in mediating resistance. This review synthesizes current knowledge, highlighting the interplay of these factors and their clinical implications. Understanding these mechanisms is crucial for developing strategies to overcome resistance and improve therapeutic outcomes in cancer patients.

Integrated analyses of multi-omic data derived from paired primary lung cancer and brain metastasis reveal the metabolic vulnerability as a novel therapeutic target

BACKGROUND

Lung cancer brain metastases (LC-BrMs) are frequently associated with dismal mortality rates in patients with lung cancer; however, standard of care therapies for LC-BrMs are still limited in their efficacy. A deep understanding of molecular mechanisms and tumor microenvironment of LC-BrMs will provide us with new insights into developing novel therapeutics for treating patients with LC-BrMs.

METHODS

Here, we performed integrated analyses of genomic, transcriptomic, proteomic, metabolomic, and single-cell RNA sequencing data which were derived from a total number of 154 patients with paired and unpaired primary lung cancer and LC-BrM, spanning four published and two newly generated patient cohorts on both bulk and single cell levels.

RESULTS

We uncovered that LC-BrMs exhibited a significantly greater intra-tumor heterogeneity. We also observed that mutations in a subset of genes were almost always shared by both primary lung cancers and LC-BrM lesions, including TTN, TP53, MUC16, LRP1B, RYR2, and EGFR. In addition, the genome-wide landscape of somatic copy number alterations was similar between primary lung cancers and LC-BrM lesions. Nevertheless, several regions of focal amplification were significantly enriched in LC-BrMs, including 5p15.33 and 20q13.33. Intriguingly, integrated analyses of transcriptomic, proteomic, and metabolomic data revealed mitochondrial-specific metabolism was activated but tumor immune microenvironment was suppressed in LC-BrMs. Subsequently, we validated our results by conducting real-time quantitative reverse transcription PCR experiments, immunohistochemistry, and multiplexed immunofluorescence staining of patients' paired tumor specimens. Therapeutically, targeting oxidative phosphorylation with gamitrinib in patient-derived organoids of LC-BrMs induced apoptosis and inhibited cell proliferation. The combination of gamitrinib plus anti-PD-1 immunotherapy significantly improved survival of mice bearing LC-BrMs. Patients with a higher expression of mitochondrial metabolism genes but a lower expression of immune genes in their LC-BrM lesions tended to have a worse survival outcome.

CONCLUSIONS

In conclusion, our findings not only provide comprehensive and integrated perspectives of molecular underpinnings of LC-BrMs but also contribute to the development of a potential, rationale-based combinatorial therapeutic strategy with the goal of translating it into clinical trials for patients with LC-BrMs.

Emerging Gene-editing nano-therapeutics for Cancer

Remarkable progress has been made in the field of genome engineering after the discovery of CRISPR/Cas9 in 2012 by Jennifer Doudna and Emmanuelle Charpentier. Compared to any other gene-editing tools, CRISPR/Cas9 attracted the attention of the scientific community because of its simplicity, specificity, and multiplex editing possibilities for which the inventors were awarded the Nobel prize for chemistry in 2020. CRISPR/Cas9 allows targeted alteration of the genomic sequence, gene regulation, and epigenetic modifications using an RNA-guided site-specific endonuclease. Though the impact of CRISPR/Cas9 was undisputed, some of its limitations led to key modifications including the use of miniature-Cas proteins, Cas9 Retron precise Parallel Editing via homologY (CRISPEY), Cas-Clover, or development of alternative methods including retron-recombineering, Obligate Mobile Element Guided Activity(OMEGA), Fanzor, and Argonaute proteins. As cancer is caused by genetic and epigenetic alterations, gene-editing was found to be highly useful for knocking out oncogenes, editing mutations to regain the normal functioning of tumor suppressor genes, knock-out immune checkpoint blockade in CAR-T cells, producing 'off-the-shelf' CAR-T cells, identify novel tumorigenic genes and functional analysis of multiple pathways in cancer, etc. Advancements in nanoparticle-based delivery of guide-RNA and Cas9 complex to the human body further enhanced the potential of CRISPR/Cas9 for clinical translation. Several studies are reported for developing novel delivery methods to enhance the tumor-specific application of CRISPR/Cas9 for anticancer therapy. In this review, we discuss new developments in novel gene editing techniques and recent progress in nanoparticle-based CRISPR/Cas9 delivery specific to cancer applications.

Association between pre-diagnosis recreational physical activity and risk of breast cancer recurrence: the California Teachers Study

PURPOSE

Studies have reported inverse associations of pre-diagnosis recreational physical activity (RPA) level with all-cause and breast cancer (BCa)-specific mortality among BCa patients. However, the association between pre-diagnosis RPA level and BCa recurrence is unclear. We investigated the association between pre-diagnosis RPA level and risk of BCa recurrence in the California Teachers Study (CTS).

METHODS

Stage I-IIIb BCa survivors (n = 6,479) were followed with median of 7.4 years, and 474 BCa recurrence cases were identified. Long-term (from high school to age at baseline questionnaire, or, age 55 years, whichever was younger) and baseline (past 3 years reported at baseline questionnaire) pre-diagnosis RPA levels were converted to metabolic equivalent of task-hours per week (MET-hrs/wk). Multivariable Cox proportional hazards models estimated hazard ratios (HRs) and 95% confidence intervals (CIs) for risk of BCa recurrence overall and by estrogen receptor (ER)/progesterone receptor (PR) status.

RESULTS

Long-term RPA was not associated with BCa recurrence risk (ptrend = 0.99). The inverse association between baseline pre-diagnosis RPA level and BCa recurrence risk was marginally significant (≥26.0 vs. <3.4 MET-hrs/wk: HR = 0.79, 95% CI = 0.60-1.03; ptrend = 0.07). However, the association became non-significant after adjusting for post-diagnosis RPA (ptrend = 0.65). An inverse association between baseline pre-diagnosis RPA level and BCa recurrence risk was observed in ER-PR- cases (≥26.0 vs. <3.4 MET-hrs/wk: HR = 0.31, 95% CI = 0.13-0.72; ptrend = 0.04), but not in ER+ or PR+ cases (ptrend = 0.97).

CONCLUSIONS

Our data indicates that the benefit of baseline RPA on BCa recurrence may differ by tumor characteristics. This information may be particularly important for populations at higher risk of ER-PR- BCa.

Nanoenzymes: A Radiant Hope for the Early Diagnosis and Effective Treatment of Breast and Ovarian Cancers

Breast and ovarian cancers, despite having chemotherapy and surgical treatment, still have the lowest survival rate. Experimental stages using nanoenzymes/nanozymes for ovarian cancer diagnosis and treatment are being carried out, and correspondingly the current treatment approaches to treat breast cancer have a lot of adverse side effects, which is the reason why researchers and scientists are looking for new strategies with less side effects. Nanoenzymes have intrinsic enzyme-like activities and can reduce the shortcomings of naturally occurring enzymes due to the ease of storage, high stability, less expensive, and enhanced efficiency. In this review, we have discussed various ways in which nanoenzymes are being used to diagnose and treat breast and ovarian cancer. For breast cancer, nanoenzymes and their multi-enzymatic properties can control the level of reactive oxygen species (ROS) in cells or tissues, for example, oxidase (OXD) and peroxidase (POD) activity can be used to generate ROS, while catalase (CAT) or superoxide dismutase (SOD) activity can scavenge ROS. In the case of ovarian cancer, most commonly nanoceria is being investigated, and also when folic acid is combined with nanoceria there are additional advantages like inhibition of beta galactosidase. Nanocarriers are also used to deliver small interfering RNA that are effective in cancer treatment. Studies have shown that iron oxide nanoparticles are actively being used for drug delivery, similarly ferritin carriers are used for the delivery of nanozymes. Hypoxia is a major factor in ovarian cancer, therefore MnO2-based nanozymes are being used as a therapy. For cancer diagnosis and screening, nanozymes are being used in sonodynamic cancer therapy for cancer diagnosis and screening, whereas biomedical imaging and folic acid gold particles are also being used for image guided treatments. Nanozyme biosensors have been developed to detect ovarian cancer. This review article summarizes a detailed insight into breast and ovarian cancers in light of nanozymes-based diagnostic and therapeutic approaches.

An orthotopic prostate cancer model for new treatment development using syngeneic or patient-derived tumors

BACKGROUND

There are limited preclinical orthotopic prostate cancer models due to the technical complexity of surgical engraftment and tracking the tumor growth in the mouse prostate gland. Orthotopic xenografts recapitulate the tumor microenvironment, tumor stromal interactions, and clinical behavior to a greater extent than xenografts grown at subcutaneous or intramuscular sites.

METHODS

This study describes a novel micro-surgical technique for orthotopically implanting intact tumors pieces from cell line derived (transgenic adenocarcinoma mouse prostate [TRAMP]-C2) or patient derived (neuroendocrine prostate cancer [NEPC]) tumors in the mouse prostate gland and monitoring tumor growth using magnetic resonance (MR) imaging.

RESULTS

The TRAMP-C2 tumors grew rapidly to a predetermined endpoint size of 10 mm within 3 weeks, whereas the NEPC tumors grew at a slower rate over 7 weeks. The tumors were readily detected by MR and confidently identified when they were approximately 2-3 mm in size. The tumors were less well-defined on CT. The TRAMP-C2 tumors were characterized by amorphous sheets of poorly differentiated cells similar to a high-grade prostatic adenocarcinoma and frequent macroscopic peritoneal and lymph node metastases. In contrast, the NEPC's displayed a neuroendocrine morphology with polygonal cells arranged in nests and solid sheets and high count. There was a local invasion of the bladder and other adjacent tissues but no identifiable metastases. The TRAMP-C2 tumors were more hypoxic than the NEPC tumors.

CONCLUSIONS

This novel preclinical orthotopic prostate cancer mouse model is suitable for either syngeneic or patient derived tumors and will be effective in developing and advancing the current selection of treatments for patients with prostate cancer.

Nanoparticle drug delivery systems responsive to tumor microenvironment: Promising alternatives in the treatment of triple-negative breast cancer

The conventional therapeutic treatment of triple-negative breast cancer (TNBC) is negatively influenced by the development of tumor cell drug resistant, and systemic toxicity of therapeutic agents due to off-target activity. In accordance with research findings, nanoparticles (NPs) responsive to the tumor microenvironment (TME) have been discovered for providing opportunities to selectively target tumor cells via active targeting or Enhanced Permeability and Retention (EPR) effect. The combination of the TME control and therapeutic NPs offers promising solutions for improving the prognosis of the TNBC because the TME actively participates in tumor growth, metastasis, and drug resistance. The NP-based systems leverage stimulus-responsive mechanisms, such as low pH value, hypoxic, excessive secretion enzyme, concentration of glutathione (GSH)/reactive oxygen species (ROS), and high concentration of Adenosine triphosphate (ATP) to combat TNBC progression. Concurrently, NP-based stimulus-responsive introduces a novel approach for drug dosage design, administration, and modification of the pharmacokinetics of conventional chemotherapy and immunotherapy drugs. This review provides a comprehensive examination of the strengths, limitations, applications, perspectives, and future expectations of both novel and traditional stimulus-responsive NP-based drug delivery systems for improving outcomes in the medical practice of TNBC. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Quantitative Analysis of the Concentration of Trifluridine in Tumor Hypoxic Regions Using a Novel Platform Combining Functional Endoscopy and Mass Spectrometry

Hypoxic regions in solid tumors are highly resistant to drugs and thus represents an obstacle in drug discovery. Currently, however, there are technical barriers in sampling human hypoxic tumors and examining drug delivery with high sensitivity and accuracy. Herein, we present a new platform combining functional endoscopy and highly sensitive liquid chromatography-mass spectrometry (LC-MS) to assess drug delivery to hypoxic regions. Because oxygen saturation endoscopic imaging (OXEI), a functional endoscopy, can evaluate lesions and hypoxia in real-time by simultaneously acquiring a pseudocolor map of oxygen saturation and conventional endoscopic images, this platform can be used to evaluate drug delivery with human samples from hypoxic regions. As the first clinical application of this platform, the relationship between hypoxic regions and the concentration of trifluridine (FTD) incorporated into DNA was evaluated in patients with advanced gastric cancer treated with FTD/tipiracil (FTD/TPI; n = 13) by obtaining and analysis of tissue samples by OXEI and LC-MS and vascular maturity index by CD31/α-SMA staining ex vivo. The results showed that the concentration of FTD was significantly higher in the normoxic region than in the hypoxic region (P < 0.05) and there were significantly more immature vessels in hypoxic regions than in normoxic regions (P < 0.05). These results indicate that the platform was sufficiently sensitive to evaluate differences in drug anabolism in different oxygenic regions of human tumor tissue. This new platform allows quantitative drug analysis in hypoxic regions and is expected to initiate a new era of drug discovery and development.

Relief of tumor hypoxia using a nanoenzyme amplifies NIR-II photoacoustic-guided photothermal therapy

Hypoxia is a critical tumor microenvironment (TME) component. It significantly impacts tumor growth and metastasis and is known to be a major obstacle for cancer therapy. Integrating hypoxia modulation with imaging-based monitoring represents a promising strategy that holds the potential for enhancing tumor theranostics. Herein, a kind of nanoenzyme Prussian blue (PB) is synthesized as a metal-organic framework (MOF) to load the second near-infrared (NIR-II) small molecule dye IR1061, which could catalyze hydrogen peroxide to produce oxygen and provide a photothermal conversion element for photoacoustic imaging (PAI) and photothermal therapy (PTT). To enhance stability and biocompatibility, silica was used as a coating for an integrated nanoplatform (SPI). SPI was found to relieve the hypoxic nature of the TME effectively, thus suppressing tumor cell migration and downregulating the expression of heat shock protein 70 (HSP70), both of which led to an amplified NIR-II PTT effect in vitro and in vivo, guided by the NIR-II PAI. Furthermore, label-free multi-spectral PAI permitted the real-time evaluation of SPI as a putative tumor treatment. A clinical histological analysis confirmed the amplified treatment effect. Hence, SPI combined with PAI could offer a new approach for tumor diagnosing, treating, and monitoring.

The microRNA-4766/VEGFA axis mediates macrophage M2-type polarization to inhibit colorectal cancer proliferation and migration

OBJECTIVE

To investigate the miR-4766/VEGFA axis in regulating M2-type macrophage polarization under hypoxia and its effect on the proliferation and migration of colorectal cancer (CRC) cells.

METHODS

The differentially expressed genes (DEGs) in macrophages before and after hypoxia treatment in the dataset GSE154427 were analyzed. microRNA (miR)-4766 and VEGFA were selected as the research objects and then detected for mRNA expression and protein level using qRT-PCR and Western blot, respectively. The expression levels of M2 macrophage markers such as CD206, CD163, and ARG1 were detected to determine the M2-type macrophage polarization. The targeted binding of miR-4766 to VEGFA was verified using Dual-luciferase reporter gene assay. CCK-8 and Transwell assays were performed, respectively, to detect the capacity of cells to proliferate and migrate. IL-10 and TGF-β levels in the conditioned medium were detected using ELISA.

RESULTS

miR-4766 was upregulated, and VEGFA was downregulated in hypoxia-treated macrophages. miR-4766 inhibited, while VEGFA promoted the polarization of M2-type macrophages. miR-4766 targeted and negatively regulated VEGFA. miR-4766 inhibited the polarization of M2-type macrophages and then suppressed CRC cell proliferation and migration via targeting VEGFA.

CONCLUSION

Restoring miR-4766 expression to inhibit VEGFA expression promised to be a potential strategy to suppress CRC development.

The expression of hypoxia inducible factor-1 alpha in diffuse large B-cell lymphoma (DLBCL) patients: a cross-sectional study in Indonesia

Introduction

Hypoxia fuels cancer growth by supporting blood vessel formation, suppressing immune response, and helping cancer cells adapt to harsh surroundings. This happens when cancer cells react to low oxygen levels by activating hypoxia inducible factor-1 alpha (HIF-1α). High levels of HIF-1α can indicate an aggressive form of cancer and resistance to treatment in diffuse large B-cell lymphoma (DLBCL) patients. This study aimed to identify which factors are linked to HIF-1α distribution using immunohistochemistry in DLBCL patients.

Method

This study conducted at a hospital in Indonesia between 2020 and 2022 aimed to investigate factors associated with HIF-1α expression in DLBCL patients. Newly diagnosed DLBCL patients were categorized into two groups based on HIF-1α distribution (<40% and ≥40%). Various factors were analyzed between the two groups using statistical tests such as χ2, Mann-Whitney U, and Spearman correlation tests.

Results

In this study, 40 participants diagnosed with DLBCL were divided into two groups based on their HIF-1α distribution. The group with HIF-1α distribution greater than or equal to 40% had a higher incidence of extranodal involvement, including primary extranodal disease, compared to the group with less than 40% distribution. This difference was statistically significant. The authors also found that haemoglobin level statistically significant (P=0.041) in this research. The Spearman test analysis showed negative correlation between haemoglobin (P = <0.05, r = -0.44) and positive correlation of soluble interleukin-2 receptor (sIL-2R) (P = <0.05, r = 0.5) with vascular endothelial growth factor (VEGF), as well as between tumour volume (P = <0.05, r = 0.37) with sIL-2R. Additionally, there was a positive correlation between VEGF and sIL-2R (P = <0.05, r= 0.5).

Conclusion

Patients with higher HIF-1α expression (≥40%) had more extranodal involvement and primary extranodal disease in this study of 40 DLBCL patients. Haemoglobin level, sIL-2R, and VEGF were also identified as potential biomarkers.

Prognostic impact of the combination of HIF‑1α and GLUT1 in patients with oesophageal squamous cell carcinoma

Oesophageal squamous cell carcinoma (ESCC) is a common type of carcinoma. Hypoxia is associated with chemo- and radio-resistance, which may lead to a poor prognosis. Hypoxia-inducible factor-1α (HIF-1α) is the main transcriptional regulator of the cellular response to low oxygen levels. Moreover, it can trigger the expression of critical genes, including glucose transporter protein type 1 (GLUT1). The aim of the present study was to evaluate the roles of HIF-1α and GLUT1 in ESCC and their usefulness as prognostic markers. HIF-1α and GLUT1 were measured in four ESCC cell lines, namely Eca109, KYSE150, TE-1 and TE-10, by western blotting following culture under normoxic and hypoxic conditions. In addition, xenograft tumors were established in mice using normoxic and hypoxic Eca109 cells and the chemosensitivity of the xenografts to 5-fluorouracil (5-FU) was evaluated. Furthermore, HIF-1α and GLUT1 were analysed by immunochemistry in the tumor tissues of patients with ESCC and the associations of their expression levels with clinicopathological parameters were investigated. The results revealed that HIF-1α and GLUT1 protein expression was weak in all four cell lines under a normoxic atmosphere but increased following culture in a hypoxic environment. In vivo, 5-FU inhibited tumor growth more strongly in normoxic Eca109 ×enografts than hypoxic Eca109 ×enografts. Higher levels of apoptosis were also detected in the normoxic Eca109 ×enografts via western blotting and TUNEL analysis. In patients with ESCC, HIF-1α expression was associated with advanced ESCC while GLUT1 expression was associated with the sex of the patients. Multivariate analysis demonstrated that HIF-1α and GLUT1 were negatively associated with progression-free survival (PFS) and overall survival (OS). Additionally, a combination of HIF-1α and GLUT1 expression was a predictor of RFS and OS in patients with ESCC without lymph node metastasis but not those with lymph node metastasis. The study demonstrated that HIF-1α and GLUT1 were strongly expressed in vitro and in xenograft models when cells were exposed to hypoxia. The simultaneous high expression of HIF-1α and GLUT1 was associated with poorer survival, and may play an important role in ESCC chemoresistance and the prognosis of ESCC.

Targeting Mitochondrial DNA Transcription by POLRMT Inhibition or Depletion as a Potential Strategy for Cancer Treatment

Transcription of the mitochondrial genome is essential for the maintenance of oxidative phosphorylation (OXPHOS) and other functions directly related to this unique genome. Considerable evidence suggests that mitochondrial transcription is dysregulated in cancer and cancer metastasis and contributes significantly to cancer cell metabolism. Recently, inhibitors of the mitochondrial DNA-dependent RNA polymerase (POLRMT) were identified as potentially attractive new anti-cancer compounds. These molecules (IMT1, IMT1B) inactivate cancer cell metabolism through reduced transcription of mitochondrially-encoded OXPHOS subunits such as ND1-5 (Complex I) and COI-IV (Complex IV). Studies from our lab have discovered small molecule regulators of the mitochondrial matrix caseinolytic protease (ClpP) as probable inhibitors of mitochondrial transcription. These compounds activate ClpP proteolysis and lead to the rapid depletion of POLRMT and other matrix proteins, resulting in inhibition of mitochondrial transcription and growth arrest. Herein we present a comparison of POLRMT inhibition and ClpP activation, both conceptually and experimentally, and evaluate the results of these treatments on mitochondrial transcription, inhibition of OXPHOS, and ultimately cancer cell growth. We discuss the potential for targeting mitochondrial transcription as a cancer cell vulnerability.

Design, Synthesis and Anticancer Evaluation of Nitroimidazole Radiosensitisers

The role of hypoxic tumour cells in resistance to radiotherapy, and in suppression of immune response, continues to endorse tumour hypoxia as a bona fide, yet largely untapped, drug target. Radiotherapy innovations such as stereotactic body radiotherapy herald new opportunities for classical oxygen-mimetic radiosensitisers. Only nimorazole is used clinically as a radiosensitiser, and there is a dearth of new radiosensitisers in development. In this report, we augment previous work to present new nitroimidazole alkylsulfonamides and we document their cytotoxicity and ability to radiosensitise anoxic tumour cells in vitro. We compare radiosensitisation with etanidazole and earlier nitroimidazole sulfonamide analogues and we identify 2-nitroimidazole and 5-nitroimidazole analogues with marked tumour radiosensitisation in ex vivo assays of surviving clonogens and with in vivo tumour growth inhibition.

Extracellular vesicles as a novel approach for breast cancer therapeutics

Breast cancer (BC) still lacks effective management approaches to control metastatic and therapy-resistant disease. Extracellular vesicles (EVs), with a diameter of 50-1000 nm, are secreted by all types of living cells, are protected by a lipid bilayer and encapsulate biological cargos including RNAs, proteins and lipids. They play an important role in intercellular communications and are significantly associated with pathological conditions. Accumulating evidence indicates that cancer cells secrete EVs and communicate with neighboring cells within the tumor microenvironment (TME), which plays an important role in BC metastasis, immune escape and chemoresistance, thus providing a new therapeutic window. EVs can stimulate angiogenesis and extracellular matrix remodeling, establish premetastatic niches, inhibit immune response and promote cancer metastasis. Recent advances have demonstrated that EVs are a potential therapeutic target or carrier and have emerged as promising strategies for BC treatment. In this review, we summarize the role of EVs in BC metastasis, chemoresistance and immune escape, which provides the foundation for developing novel therapeutic approaches. We also focus on current EV-based drug delivery strategies in BC and EV cargo-targeted BC therapy and discuss the limitations and future perspectives of EV-based drug delivery in BC.

Bacteria-Driven Tumor Microenvironment-Sensitive Nanoparticles Targeting Hypoxic Regions Enhances the Chemotherapy Outcome of Lung Cancer

Background

Chemotherapy still plays a dominant role in cancer treatment. However, the inability of conventional chemotherapeutic drugs to reach the hypoxic zone of solid tumors significantly weakens their efficacy. Bacteria-mediated drug delivery systems can be an effective targeting strategy for improving the therapeutic outcomes in cancer. Anaerobic bacteria have the unique ability to selectively transport drug loads to the hypoxic regions of tumors.

Methods

We designed a Bifidobacterium infantis (Bif)-based biohybrid (Bif@PDA-PTX-NPs) to deliver polydopamine (PDA)-coated paclitaxel nanoparticles (PTX-NPs) to tumor tissues.

Results

The self-driven Bif@PDA-PTX-NPs maintained the toxicity of PTX as well as the hypoxic homing tendency of Bif. Furthermore, Bif@PDA-PTX-NPs significantly inhibited the growth of A549 xenografts in nude mice, and prolonged the survival of the tumor-bearing mice compared to the other PTX formulations without any systemic or localized toxicity.

Conclusion

The Bif@PDA-PTX-NPs biohybrids provide a new therapeutic strategy for targeted chemotherapy to solid tumors.

Fluid-sensitive migration mechanisms predict association between metastasis and high interstitial fluid pressure in pancreatic cancer

A remarkable feature in pancreatic cancer is the propensity to metastasize early, even for small, early stage cancers. We use a computer-based pancreatic model to simulate tumor progression behavior where fluid-sensitive migration mechanisms are accounted for as a plausible driver for metastasis. The model has been trained to comply with in vitro results to determine input parameters that characterize the migration mechanisms. To mimic previously studied preclinical xenografts we run the computer model informed with an ensemble of stochastic-generated realizations of unknown parameters related to tumor microenvironment only constrained such that pathological realistic values for interstitial fluid pressure (IFP) are obtained. The in silico model suggests the occurrence of a steady production of small clusters of cancer cells that detach from the primary tumor and form isolated islands and thereby creates a natural prerequisite for a strong invasion into the lymph nodes and venous system. The model predicts that this behavior is associated with high interstitial fluid pressure (IFP), consistent with published experimental findings. The continuum-based model is the first to explain published results for preclinical models which have reported associations between high IFP and high metastatic propensity and thereby serves to shed light on possible mechanisms behind the clinical aggressiveness of pancreatic cancer.

The Study of the Extracellular Matrix in Chronic Inflammation: A Way to Prevent Cancer Initiation?

Bidirectional communication between cells and their microenvironment has a key function in normal tissue homeostasis, and in disease initiation, progression and a patient's prognosis, at the very least. The extracellular matrix (ECM), as an element of all tissues and cellular microenvironment, is a frequently overlooked component implicated in the pathogenesis and progression of several diseases. In the inflammatory microenvironment (IME), different alterations resulting from remodeling processes can affect ECM, progressively inducing cancer initiation and the passage toward a tumor microenvironment (TME). Indeed, it has been demonstrated that altered ECM components interact with a variety of surface receptors triggering intracellular signaling that affect cellular pathways in turn. This review aims to support the notion that the ECM and its alterations actively participate in the promotion of chronic inflammation and cancer initiation. In conclusion, some data obtained in cancer research with the employment of decellularized ECM (dECM) models are described. The reported results encourage the application of dECM models to investigate the short circuits contributing to the creation of distinct IME, thus representing a potential tool to avoid the progression toward a malignant lesion.

Multifunctional Oxygenated Particles for Targeted Cancer Drug Delivery and Evaluation with Darkfield Hyperspectral Imaging

We propose a novel multifunctional nanocarrier system for targeted drug delivery for lung cancer theranostics. Oxygenated particles (OPs) synthesized with an oxygen-encapsulating carboxymethyl cellulose shell were used as a platform to deliver oxygen to the hypoxic tumor microenvironment. The OPs synthesized could also be conjugated with ligands (e.g., antibodies) to target cancer cells expressing the corresponding antigens to deliver a drug, doxorubicin. In vitro testing of functionalized OPs showed increased efficacy of doxorubicin against the proliferation of lung cancer cells. Both confocal fluorescence imaging and darkfield microscopy hyperspectral imaging validated the OP complex and its efficient targeting of specific cells to deliver the therapeutic. The nanocarrier platform developed can also serve as a diagnostic imaging reagent as demonstrated by darkfield microscopy. Results show that the theranostic OPs developed with multifunctional modalities enabled targeted drug delivery with improved efficacy and tracking of drug delivery vehicles by imaging.

Exploration of various roles of hypoxia genes in osteosarcoma

Osteosarcoma is a primary malignant tumor that often metastasizes in orthopedic diseases. Although multi-drug chemotherapy and surgical treatment have significantly improved the survival and prognosis of patients with osteosarcoma, the survival rate is still very low due to frequent metastases in patients with osteosarcoma. In-depth exploration of the relationship between various influencing factors of osteosarcoma is very important for screening promising therapeutic targets. This study used multivariate COX regression analysis to select the hypoxia genes SLC2A1 and FBP1 in patients with osteosarcoma, and used the expression of these two genes to divide the patients with osteosarcoma into high-risk and low-risk groups. Then, we first constructed a prognostic model based on the patient's risk value and compared the survival difference between the high expression group and the low expression group. Second, in the high expression group and the low expression group, compare the differences in tumor invasion and inflammatory gene expression between the two groups of immune cells. Finally, the ferroptosis-related genes with differences between the high expression group and the low expression group were screened, and the correlation between these genes was analyzed. In the high-risk group, immune cells with higher tumor invasiveness, macrophages M0 and immune cells with lower invasiveness included: mast cell resting, regulatory T cells (Tregs) and monocytes. Finally, among genes related to ferroptosis, we found AKR1C2, AKR1C1 and ALOX15 that may be related to hypoxia. These ferroptosis-related genes were discovered for the first time in osteosarcoma. Among them, the hypoxia gene FBP1 is positively correlated with the ferroptosis genes AKR1C1 and ALOX15, and the hypoxia gene SLC2A1 is negatively correlated with the ferroptosis genes AKR1C2, AKR1C1 and ALOX15. This study constructed a prognostic model based on hypoxia-related genes SLC2A1 and FBP1 in patients with osteosarcoma, and explored their correlation with immune cells, inflammatory markers and ferroptosis-related genes. This indicates that SLC2A1 and FBP1 are promising targets for osteosarcoma research.

Integrating Radiosensitivity Gene Signature Improves Glioma Outcome and Radiotherapy Response Prediction

Response to radiotherapy (RT) in gliomas varies widely between patients. It is necessary to identify glioma-associated radiosensitivity gene signatures for clinically stratifying patients who will benefit from adjuvant radiotherapy after glioma surgery. Methods: Chinese Glioma Genome Atlas (CGGA) and the Cancer Genome Atlas (TCGA) glioma patient datasets were used to validate the predictive potential of two published biomarkers, the radiosensitivity index (RSI) and 31-gene signature (31-GS). To adjust these markers for the characteristics of glioma, we integrated four new glioma-associated radiosensitivity predictive indexes based on RSI and 31-GS by the Cox analysis and Least Absolute Shrinkage and Selection Operator (LASSO) regression analysis. A receiver operating characteristic (ROC) curve, integrated discrimination improvement (IDI), and net reclassification improvement (NRI) were used to compare the radiosensitivity predictive ability of these six gene signatures. Subgroup analysis was used to evaluate the discriminative capacity of those gene signatures in identifying radiosensitive patients, and a nomogram was built to improve the histological grading system. Gene Ontology (GO) analysis and Gene Set Enrichment Analysis (GSEA) were used to explore related biological processes. Results: We validated and compared the predictive potential of two published predictive indexes. The AUC area of 31-GS was higher than that of RSI. Based on the RSI and 31-GS, we integrated four new glioma-associated radiosensitivity predictive indexes—PI10, PI12, PI31 and PI41. Among them, a 12-gene radiosensitivity predictive index (PI12) showed the most promising predictive performance and discriminative capacity. Examination of a nomogram created from clinical features and PI12 revealed that its predictive capacity was superior to the traditional WHO classification system. (C-index: 0.842 vs. 0.787, p ≤ 2.2 × 10⁻¹⁶) The GO analysis and GSEA showed that tumors with a high PI12 score correlated with various aspects of the malignancy of glioma. Conclusions: The glioma-associated radiosensitivity gene signature PI12 is a promising radiosensitivity predictive biomarker for guiding effective personalized radiotherapy for gliomas.

Preliminary study of hypoxia markers in diffuse large B‑cell lymphoma

While the association of hypoxia has been established in various types of solid cancers, little is known about its presence and existence in diffuse large B-cell lymphoma (DLBCL). The purpose of the present study was to evaluate the expression of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor A (VEGF-A) in DLBCL and to analyze the association of these factors with several clinical and pathological characteristics. The immunohistochemical protein expression of HIF-1α and VEGF-A was investigated in 34 de novo DLBCL tumor samples from January 2017 to December 2017 from the Department of Hematology/Medical Oncology and Anatomical Pathology at Dr Kariadi Hospital (Semarang, Indonesia). The present study revealed by using immunohistochemistry (IHC), that hypoxic markers were overexpressed (88.2% for both HIF-1α and VEGF-A) in the vast majority of patients with DLBCL. Only in 4 tumors, was HIF-1α expression normal, and interestingly VEGF-A was negative as well. There was a significant correlation in the intensity of staining of HIF-1α and VEGF-A using our custom scoring system in surgically resected tissues (r=0.475; P=0.005). Both HIF-1α and VEGF-A were also associated to serum LDH and tumor diameter. Collectively, HIF-1α and VEGF-A were predominantly expressed in the majority of DLBCL tumor cells. The findings of the present study indicate the existence of hypoxia in DLBCL tumors similar to numerous solid cancers, and thus warrants further investigation to clarify its role as a potential pathogenic or prognostic marker in this type of hematological cancer.

The close interaction between hypoxia-related proteins and metastasis in pancarcinomas

Many primary-tumor subregions exhibit low levels of molecular oxygen and restricted access to nutrients due to poor vascularization in the tissue, phenomenon known as hypoxia. Hypoxic tumors are able to regulate the expression of certain genes and signaling molecules in the microenvironment that shift it towards a more aggressive phenotype. The transcriptional landscape of the tumor favors malignant transformation of neighboring cells and their migration to distant sites. Herein, we focused on identifying key proteins that participate in the signaling crossroads between hypoxic environment and metastasis progression that remain poorly defined. To shed light on these mechanisms, we performed an integrated multi-omics analysis encompassing genomic/transcriptomic alterations of hypoxia-related genes and Buffa hypoxia scores across 17 pancarcinomas taken from the PanCancer Atlas project from The Cancer Genome Atlas consortium, protein-protein interactome network, shortest paths from hypoxia-related proteins to metastatic and angiogenic phenotypes, and drugs involved in current clinical trials to treat the metastatic disease. As results, we identified 30 hypoxia-related proteins highly involved in metastasis and angiogenesis. This set of proteins, validated with the MSK-MET Project, could represent key targets for developing therapies. The upregulation of mRNA was the most prevalent alteration in all cancer types. The highest frequencies of genomic/transcriptomic alterations and hypoxia score belonged to tumor stage 4 and positive metastatic status in all pancarcinomas. The most significantly associated signaling pathways were HIF-1, PI3K-Akt, thyroid hormone, ErbB, FoxO, mTOR, insulin, MAPK, Ras, AMPK, and VEGF. The interactome network revealed high-confidence interactions among hypoxic and metastatic proteins. The analysis of shortest paths revealed several ways to spread metastasis and angiogenesis from hypoxic proteins. Lastly, we identified 23 drugs enrolled in clinical trials focused on metastatic disease treatment. Six of them were involved in advanced-stage clinical trials: aflibercept, bevacizumab, cetuximab, erlotinib, ipatasertib, and panitumumab.

Synthesis of a 2-nitroimidazole derivative N-(4-[18F]fluorobenzyl)-2-(2-nitro-1H-imidazol-1-yl)-acetamide ([18 F]FBNA) as PET radiotracer for imaging tumor hypoxia

BACKGROUND

Tissue hypoxia is a pathological condition characterized by reducing oxygen supply. Hypoxia is a hallmark of tumor environment and is commonly observed in many solid tumors. Non-invasive imaging techniques like positron emission tomography (PET) are at the forefront of detecting and monitoring tissue hypoxia changes in vivo.

RESULTS

We have developed a novel ¹⁸F-labeled radiotracer for hypoxia PET imaging based on cytotoxic agent benznidazole. Radiotracer N-(4-[¹⁸F]fluorobenzyl)-2-(2-nitro-1H-imidazol-1-yl)acetamide ([¹⁸F]FBNA) was synthesized through acylation chemistry with readily available 4-[¹⁸F]fluorobenzyl amine. Radiotracer [¹⁸F]FBNA was obtained in good radiochemical yields (47.4 ± 5.3%) and high radiochemical purity (> 95%). The total synthesis time was 100 min, including HPLC purification and the molar activity was greater than 40 GBq/µmol. Radiotracer [¹⁸F]FBNA was stable in saline and mouse serum for 6 h. [¹⁸F]FBNA partition coefficient (logP = 1.05) was found to be more lipophilic than [¹⁸F]EF-5 (logP = 0.75), [¹⁸F]FMISO (logP = 0.4) and [¹⁸F]FAZA (logP =  - 0.4). In vitro studies showed that [¹⁸F]FBNA accumulates in gastric cancer cell lines AGS and MKN45 under hypoxic conditions.

CONCLUSIONS

Hence, [¹⁸F]FBNA represents a novel and easy-to-prepare PET radioligand for imaging hypoxia.

Hypoxia-directed tumor targeting of CRISPR-Cas9 and HSV-TK suicide gene therapy using lipid nanoparticles

Hypoxia is a characteristic feature of solid tumors that contributes to tumor aggressiveness and is associated with resistance to cancer therapy. The hypoxia inducible factor-1 (HIF-1) transcription factor complex mediates hypoxia-specific gene expression by binding to hypoxia-responsive element (HRE) sequences within the promoter of target genes. HRE-driven expression of therapeutic cargo has been widely explored as a strategy to achieve cancer-specific gene expression. By utilizing this system, we achieve hypoxia-specific expression of two therapeutically relevant cargo elements: the herpes simplex virus thymidine kinase (HSV-tk) suicide gene and the CRISPR-Cas9 nuclease. Using an expression vector containing five copies of the HRE derived from the vascular endothelial growth factor gene, we are able to show high transgene expression in cells in a hypoxic environment, similar to levels achieved using the cytomegalovirus (CMV) and CBh promoters. Furthermore, we are able to deliver our therapeutic cargo to tumor cells with high efficiency using plasmid-packaged lipid nanoparticles (LNPs) to achieve specific killing of tumor cells in hypoxic conditions while maintaining tight regulation with no significant changes to cell viability in normoxia.

Significance of Specific Oxidoreductases in the Design of Hypoxia-Activated Prodrugs and Fluorescent Turn Off–On Probes for Hypoxia Imaging

Simple Summary

Hypoxia-activated prodrugs (HAPs), selectively reduced by specific oxidoreductases under hypoxic conditions, form cytotoxic agents damaging the local cancer cells. On the basis of the reported clinical data concerning several HAPs, one can draw conclusions regarding their preclinical attractiveness and, regrettably, the low efficacy of Phase III clinical trials. Clinical failure may be explained, inter alia, by the lack of screening of patients on the basis of tumor hypoxia and low availability of specific oxidoreductases involved in HAP activation. There is surprisingly little information on the quantification of these enzymes in cells or tissues, compared to the advanced research associated with the use of HAPs. Our knowledge about the expression and activity of these enzymes in various cancer cell lines under hypoxic conditions is inadequate. Only in a few cases were researchers able to demonstrate the differences in the expression or activity of selected oxidoreductases, depending on the oxygen concentration. Additionally, it was cell line dependent. More systematic studies are required. The optical probes, based on turning on the fluorescence emission upon irreversible reduction catalyzed by the overexpressed oxidoreductases, can be helpful in this type of research. Ultimately, such sensors can estimate both the oxidoreductase activity and the degree of oxygenation in one step. To achieve this goal, their response must be correlated with the expression or activity of enzymes potentially involved in turning on their emissions, as determined by biochemical methods. In conclusion, the incorporation of biomarkers to identify hypoxia is a prerequisite for successful HAP therapies. However, it is equally important to assess the level of specific oxidoreductases required for their activation.

Abstract

Hypoxia is one of the hallmarks of the tumor microenvironment and can be used in the design of targeted therapies. Cellular adaptation to hypoxic stress is regulated by hypoxia-inducible factor 1 (HIF-1). Hypoxia is responsible for the modification of cellular metabolism that can result in the development of more aggressive tumor phenotypes. Reduced oxygen concentration in hypoxic tumor cells leads to an increase in oxidoreductase activity that, in turn, leads to the activation of hypoxia-activated prodrugs (HAPs). The same conditions can convert a non-fluorescent compound into a fluorescent one (fluorescent turn off–on probes), and such probes can be designed to specifically image hypoxic cancer cells. This review focuses on the current knowledge about the expression and activity of oxidoreductases, which are relevant in the activation of HAPs and fluorescent imaging probes. The current clinical status of HAPs, their limitations, and ways to improve their efficacy are briefly discussed. The fluorescence probes triggered by reduction with specific oxidoreductase are briefly presented, with particular emphasis placed on those for which the correlation between the signal and enzyme expression determined with biochemical methods is achievable.

BHLHE41 Overexpression Alleviates the Malignant Behavior of Colon Cancer Cells Induced by Hypoxia via Modulating HIF-1α/EMT Pathway

Objective. BHLHE41 has been shown to be a marker of tumorigenesis. Colon cancer (CC) is a common malignant tumor of colonic mucosa. This study mainly explored the mechanism of BHLHE41 in alleviating malignant behavior of hypoxia-induced CC cells. Methods. The levels of BHLHE41 in CC and normal cell lines were tested by Western blot and qRT-PCR. After, CC cells were subjected to hypoxia treatment and BHLHE41 overexpression transfection, and the BHLHE41 expression, the effect of BHLHE41 on CC cell viability, apoptosis, migration, and invasion and cell cycle were tested by qRT-PCR and relevant cell functional experiments. HIF-1α and epithelial-mesenchymal transition- (EMT-) related proteins were tested by Western blot. Moreover, CC tumor-bearing model was established in nude mice, and the effect of BHLHE41 on the tumor was evaluated by measuring the tumor volume and weight. Then, the expressions of BHLHE41 and EMT-related proteins were detected by immunohistochemistry and Western blot. Results. Western blot and qRT-PCR showed that BHLHE41 was lowly expressed in CC cells. BHLHE41 overexpression could inhibit the hypoxia-induced CC cell viability, migration, and invasion, induce apoptosis, and alter cell cycle. Besides, BHLHE41 overexpression could enhance the levels of E-cadherin but reduce the levels of HIF-1α, N-cadherin, vimentin, and MMP9 in hypoxia-induced CC cells. Moreover, BHLHE41 overexpression reduced tumor volume, weight, and EMT-related proteins levels in tumor tissues. Conclusions. BHLHE41 overexpression could mitigate the malignant behavior of hypoxia-induced CC via modulating the HIF-1α/EMT pathway.

Modulating Tumour Hypoxia in Prostate Cancer Through Exercise: The Impact of Redox Signalling on Radiosensitivity

Prostate cancer is a complex disease affecting millions of men globally. Radiotherapy (RT) is a common treatment modality although treatment efficacy is dependent upon several features within the tumour microenvironment (TME), especially hypoxia. A hypoxic TME heightens radioresistance and thus disease recurrence and treatment failure continues to pose important challenges. However, the TME evolves under the influence of factors in systemic circulation and cellular crosstalk, underscoring its potential to be acutely and therapeutically modified. Early preclinical evidence suggests exercise may affect tumour growth and some of the benefits drawn, could act to radiosensitise tumours to treatment. Intracellular perturbations in skeletal muscle reactive oxygen species (ROS) stimulate the production of numerous factors that can exert autocrine, paracrine, and endocrine effects on the prostate. However, findings supporting this notion are limited and the associated mechanisms are poorly understood. In light of this preclinical evidence, we propose systemic changes in redox signalling with exercise activate redox-sensitive factors within the TME and improve tumour hypoxia and treatment outcomes, when combined with RT. To this end, we suggest a connection between exercise, ROS and tumour growth kinetics, highlighting the potential of exercise to sensitise tumour cells to RT, and improve treatment efficacy.

Bacteria-driven hypoxia targeting delivery of chemotherapeutic drug proving outcome of breast cancer

Local hypoxia is a common feature of many solid tumors and may lead to unsatisfactory chemotherapy outcomes. Anaerobic bacteria that have an affinity to hypoxic areas can be used to achieve targeted drug delivery in tumor tissues. In this study, we developed a biocompatible bacteria/nanoparticles biohybrid (Bif@DOX-NPs) platform that employs the anaerobic Bifidobacterium infantis (Bif) to deliver adriamycin-loaded bovine serum albumin nanoparticles (DOX-NPs) into breast tumors. The Bif@DOX-NPs retained the targeting ability of B. infantis to hypoxic regions, as well as the cytotoxicity of DOX. The biohybrids were able to actively colonize the hypoxic tumors and significantly increased drug accumulation at the tumor site. The DOX concentration in the tumor masses colonized by Bif@DOX-NPs was 4 times higher than that in the free DOX-treated tumors, which significantly prolonged the median survival of the tumor-bearing mice to 69 days and reduced the toxic side-effects of DOX. Thus, anaerobic bacteria-based biohybrids are a highly promising tool for the targeted treatment of solid tumors with inaccessible hypoxic regions.

Stress Responses as Master Keys to Epigenomic Changes in Transcriptome and Metabolome for Cancer Etiology and Therapeutics

From initiation through progression, cancer cells are subjected to a magnitude of endogenous and exogenous stresses, which aid in their neoplastic transformation. Exposure to these classes of stress induces imbalance in cellular homeostasis and, in response, cancer cells employ informative adaptive mechanisms to rebalance biochemical processes that facilitate survival and maintain their existence. Different kinds of stress stimuli trigger epigenetic alterations in cancer cells, which leads to changes in their transcriptome and metabolome, ultimately resulting in suppression of growth inhibition or induction of apoptosis. Whether cancer cells show a protective response to stress or succumb to cell death depends on the type of stress and duration of exposure. A thorough understanding of epigenetic and molecular architecture of cancer cell stress response pathways can unveil a plethora of information required to develop novel anticancer therapeutics. The present view highlights current knowledge about alterations in epigenome and transcriptome of cancer cells as a consequence of exposure to different physicochemical stressful stimuli such as reactive oxygen species (ROS), hypoxia, radiation, hyperthermia, genotoxic agents, and nutrient deprivation. Currently, an anticancer treatment scenario involving the imposition of stress to target cancer cells is gaining traction to augment or even replace conventional therapeutic regimens. Therefore, a comprehensive understanding of stress response pathways is crucial for devising and implementing novel therapeutic strategies.

A multi-omics deep learning model for hypoxia phenotype to predict tumor aggressiveness and prognosis in uveal melanoma for rationalized hypoxia-targeted therapy

Uveal melanoma (UM) represents the most common primary intraocular malignancy in adults and is characterized by aggressive behaviors and a lack of targeted therapies. Hypoxia-targeted therapy has become a promising new therapeutic strategy in tumors. Therefore, a better understanding of the tumor hypoxia microenvironment is critical to improve the treatment efficacy of UM. In this study, we conducted an extensive multi-omics analysis to explore the heterogeneity and prognostic significance of the hypoxia microenvironment. We found that UM revealed the most significant degree of intertumoral heterogeneity in hypoxia by quantifying tumor hypoxia compared with other solid tumor types. Then we systematically correlated the hypoxia phenotypes with clinicopathological features and found that hypoxic UM tumors were associated with an increased risk of metastasis, more aggressive phenotypes, and unfavorable clinical outcomes. Integrative multi-omics analyses identified multidimensional molecular alterations related to hypoxia phenotypes, including elevated genome instability, co-occurring of 8q arm gains and loss of chromosome 3, and BAP1 mutations. Furthermore, hypoxic UM tumors could be characterized by increased CD8+ T cell infiltration and decreased naïve B cell and dysregulated metabolic pathways. Finally, we introduced DNN2HM, an interpretable deep neural network model to decode hypoxia phenotypes from multi-omics data. We showed that the DNN2HM improves hypoxia phenotype prediction and robustly predicts tumor aggressiveness and prognosis in different multi-center datasets. In conclusion, our study provides novel insight into UM tumor microenvironment, which may have clinical implications for future rationalized hypoxia-targeted therapy.

Investigation of atovaquone-induced spatial changes in tumour hypoxia assessed by hypoxia PET/CT in non-small cell lung cancer patients

BACKGROUND

Tumour hypoxia promotes an aggressive tumour phenotype and enhances resistance to anticancer treatments. Following the recent observation that the mitochondrial inhibitor atovaquone increases tumour oxygenation in NSCLC, we sought to assess whether atovaquone affects tumour subregions differently depending on their level of hypoxia.

METHODS

Patients with resectable NSCLC participated in the ATOM trial (NCT02628080). Cohort 1 (n = 15) received atovaquone treatment, whilst cohort 2 (n = 15) did not. Hypoxia-related metrics, including change in mean tumour-to-blood ratio, tumour hypoxic volume, and fraction of hypoxic voxels, were assessed using hypoxia PET imaging. Tumours were divided into four subregions or distance categories: edge, outer, inner, and centre, using MATLAB.

RESULTS

Atovaquone-induced reduction in tumour hypoxia mostly occurred in the inner and outer tumour subregions, and to a lesser extent in the centre subregion. Atovaquone did not seem to act in the edge subregion, which was the only tumour subregion that was non-hypoxic at baseline. Notably, the most intensely hypoxic tumour voxels, and therefore the most radiobiologically resistant areas, were subject to the most pronounced decrease in hypoxia in the different subregions.

CONCLUSIONS

This study provides insights into the action of atovaquone in tumour subregions that help to better understand its role as a novel tumour radiosensitiser.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT0262808. Registered 11th December 2015, https://clinicaltrials.gov/ct2/show/NCT02628080.

Impact of PET scanner non-linearity on the estimation of hypoxic fraction in cervical cancer patients

BACKGROUND

Tumor hypoxia is defined as a low oxygen level in tissue and is associated with poor clinical outcome after chemo-/radiotherapy and surgery in many solid tumor types. Positron Emission Tomography (PET) imaging provides a non-invasive means of measuring local variations in the uptake of hypoxia-targeted agents (e.g. FAZA or FMISO). Accurate quantification of uptake is critically dependent on the PET scanner's linear count rate performance. In the context of cervix cancer, high PET agent accumulation in the bladder, low uptake in the tumor, and their relative proximity makes an accurate quantification of the tumor's hypoxic fraction challenging. The purpose of this study was to estimate the impact of PET scanner non-linearity on PET-based estimation of hypoxic fraction.

MATERIAL AND METHODS

The impact of PET scanner non-linearity effect was assessed with a NEMA body phantom, using the cylinder as the "bladder-mimicking" compartment and the water filled background as a surrogate region for the tumor. A simple model of the non-linearity effect was then applied to a set of patient-derived FAZA-PET scans (N = 38) to estimate the impact of the non-linearity on the calculated hypoxic fraction (HF) for each patient.

RESULTS

The NEMA body phantom measurements revealed a substantial overestimate of activity outside the injected "bladder mimicking" cylinder compartment. This uptake resulted in an overestimate in activity between 1.9 and 0.3 kBq/cc corresponding to distances from 1.0 - 7.0 cm from the cylinder. In the patient-derived PET images, the bladder-to-tumor distance ranged between 1.0 and 3.0 cm. For the 38 patients analyzed, the HF was demonstrated to decrease by 1.1-75.0 % [median 27.2 %] depending on distance and relative uptake levels. Additionally, the magnitude of the effect of the non-linearity was found to depend on the pre-scanning hydration protocol employed (p = 0.0065).

CONCLUSION

Hypoxia imaging of tumors of the cervix is challenging due to patient specific activity accumulation in the bladder and the non-linear response of PET scanner performance. This can result in a substantial overestimate of the calculated hypoxic fraction in cervical tumors. Additional effort needs to be invested to improve the linearity of PET scanners in anatomical regions proximal to the bladder.

PRL-3 dephosphorylates p38 MAPK to promote cell survival under stress

Hypoxia within the tumor microenvironment, which leads to excessive ROS and genomic instability, is one of the hallmarks of cancer, contributing to self-renewal capability, metastasis, and radio-chemotherapy resistance. PRL-3 is an oncoprotein involved in various pro-survival signaling pathways, such as Ras/Erk, PI3K/Akt, Src/STAT, mTORC1 and JAK/STAT. However, there is little evidence connecting PRL-3-mediated apoptosis resistance to tumor microenvironmental stress. In this study, by profiling the PRL-3 expression of multiple tumor types retrieved from public databases (TCGA and NCBI GEO), we confirmed the oncogenic function of PRL-3 and found an intriguing connection between PRL-3 expression and tumor hypoxia signature genes. Moreover, by using CoCl₂, a hypoxia mimetic and ROS inducer, we discovered that cells stably expressing PRL-3, but not catalytically-inactive mutant PRL-3 C104S, showed significant resistance to CoCl₂ -induced apoptosis. This resistance to apoptosis was found to depend on p38 MAPK signaling and was further confirmed in other conditions of microenvironmental stress, including UV, H₂O₂ and hypoxia. Mechanistically, we proved that PRL-3 is a direct phosphatase of p38 MAPK under stressed conditions. Additionally, in mouse models of tumor metastasis, higher lung metastatic burden and lower p38 MAPK phosphorylation were found in mice seeded with GFP-PRL-3 expressing cells compared with those seeded with GFP-Ctrl cells. Taken together, our study identified a critical role of RPL-3 in tumorigenesis by negatively regulating p38 MAPK activity in order to facilitate tumor cell adaptation to a hypoxic stressed tumor microenvironment and suggests that PRL-3 could serve as a promising novel therapeutic target for cancer patients.

Restoring Tumour Selectivity of the Bioreductive Prodrug PR-104 by Developing an Analogue Resistant to Aerobic Metabolism by Human Aldo-Keto Reductase 1C3

PR-104 is a phosphate ester pre-prodrug that is converted in vivo to its cognate alcohol, PR-104A, a latent alkylator which forms potent cytotoxins upon bioreduction. Hypoxia selectivity results from one-electron nitro reduction of PR-104A, in which cytochrome P450 oxidoreductase (POR) plays an important role. However, PR-104A also undergoes ‘off-target’ two-electron reduction by human aldo-keto reductase 1C3 (AKR1C3), resulting in activation in oxygenated tissues. AKR1C3 expression in human myeloid progenitor cells probably accounts for the dose-limiting myelotoxicity of PR-104 documented in clinical trials, resulting in human PR-104A plasma exposure levels 3.4- to 9.6-fold lower than can be achieved in murine models. Structure-based design to eliminate AKR1C3 activation thus represents a strategy for restoring the therapeutic window of this class of agent in humans. Here, we identified SN29176, a PR-104A analogue resistant to human AKR1C3 activation. SN29176 retains hypoxia selectivity in vitro with aerobic/hypoxic IC50 ratios of 9 to 145, remains a substrate for POR and triggers γH2AX induction and cell cycle arrest in a comparable manner to PR-104A. SN35141, the soluble phosphate pre-prodrug of SN29176, exhibited superior hypoxic tumour log cell kill (>4.0) to PR-104 (2.5–3.7) in vivo at doses predicted to be achievable in humans. Orthologues of human AKR1C3 from mouse, rat and dog were incapable of reducing PR-104A, thus identifying an underlying cause for the discrepancy in PR-104 tolerance in pre-clinical models versus humans. In contrast, the macaque AKR1C3 gene orthologue was able to metabolise PR-104A, indicating that this species may be suitable for evaluating the toxicokinetics of PR-104 analogues for clinical development. We confirmed that SN29176 was not a substrate for AKR1C3 orthologues across all four pre-clinical species, demonstrating that this prodrug analogue class is suitable for further development. Based on these findings, a prodrug candidate was subsequently identified for clinical trials.

Atovaquone-HSA nano-drugs enhance the efficacy of PD-1 blockade immunotherapy by alleviating hypoxic tumor microenvironment

Background

Hypoxia is inherent character of most solid malignancies, leading to the failure of chemotherapy, radiotherapy and immunotherapy. Atovaquone, an anti-malaria drug, can alleviate tumor hypoxia by inhibiting mitochondrial complex III activity. The present study exploits atovaquone/albumin nanoparticles to improve bioavailability and tumor targeting of atovaquone, enhancing the efficacy of anti-PD-1 therapy by normalizing tumor hypoxia.

Methods

We prepared atovaquone-loaded human serum albumin (HSA) nanoparticles stabilized by intramolecular disulfide bonds, termed HSA-ATO NPs. The average size and zeta potential of HSA-ATO NPs were measured by particle size analyzer. The morphology of HSA-ATO NPs was characterized by transmission electron microscope (TEM). The bioavailability and safety of HSA-ATO NPs were assessed by animal experiments. Flow cytometry and ELISA assays were used to evaluate tumor immune microenvironment.

Results

Our data first verified that atovaquone effectively alleviated tumor hypoxia by inhibiting mitochondrial activity both in vitro and in vivo, and successfully encapsulated atovaquone in vesicle with albumin, forming HSA-ATO NPs of approximately 164 nm in diameter. We then demonstrated that the HSA-ATO NPs possessed excellent bioavailability, tumor targeting and a highly favorable biosafety profile. When combined with anti-PD-1 antibody, we observed that HSA-ATO NPs strongly enhanced the response of mice bearing tumor xenografts to immunotherapy. Mechanistically, HSA-ATO NPs promoted intratumoral CD8⁺ T cell recruitment by alleviating tumor hypoxia microenvironment, thereby enhancing the efficacy of anti-PD-1 immunotherapy.

Conclusions

Our data provide strong evidences showing that HSA-ATO NPs can serve as safe and effective nano-drugs to enhance cancer immunotherapy by alleviating hypoxic tumor microenvironment.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01034-9.

More Than Meets the Eye Regarding Cancer Metabolism

In spite of the continuous improvement in our knowledge of the nature of cancer, the causes of its formation and the development of new treatment methods, our knowledge is still incomplete. A key issue is the difference in metabolism between normal and cancer cells. The features that distinguish cancer cells from normal cells are the increased proliferation and abnormal differentiation and maturation of these cells, which are due to regulatory changes in the emerging tumour. Normal cells use oxidative phosphorylation (OXPHOS) in the mitochondrion as a major source of energy during division. During OXPHOS, there are 36 ATP molecules produced from one molecule of glucose, in contrast to glycolysis which provides an ATP supply of only two molecules. Although aerobic glucose metabolism is more efficient, metabolism based on intensive glycolysis provides intermediate metabolites necessary for the synthesis of nucleic acids, proteins and lipids, which are in constant high demand due to the intense cell division in cancer. This is the main reason why the cancer cell does not "give up" on glycolysis despite the high demand for energy in the form of ATP. One of the evolving trends in the development of anti-cancer therapies is to exploit differences in the metabolism of normal cells and cancer cells. Currently constructed therapies, based on cell metabolism, focus on the attempt to reprogram the metabolic pathways of the cell in such a manner that it becomes possible to stop unrestrained proliferation.

A General Overview on the Hyperbaric Oxygen Therapy: Applications, Mechanisms and Translational Opportunities

Hyperbaric oxygen therapy (HBOT) consists of using of pure oxygen at increased pressure (in general, 2-3 atmospheres) leading to augmented oxygen levels in the blood (Hyperoxemia) and tissue (Hyperoxia). The increased pressure and oxygen bioavailability might be related to a plethora of applications, particularly in hypoxic regions, also exerting antimicrobial, immunomodulatory and angiogenic properties, among others. In this review, we will discuss in detail the physiological relevance of oxygen and the therapeutical basis of HBOT, collecting current indications and underlying mechanisms. Furthermore, potential areas of research will also be examined, including inflammatory and systemic maladies, COVID-19 and cancer. Finally, the adverse effects and contraindications associated with this therapy and future directions of research will be considered. Overall, we encourage further research in this field to extend the possible uses of this procedure. The inclusion of HBOT in future clinical research could be an additional support in the clinical management of multiple pathologies.

Engineering Tools for Regulating Hypoxia in Tumour Models

Major advances in the field of genomic technologies have led to an improvement in cancer diagnosis, classification and prognostication. However, many cancers remain incurable due to the development of drug resistance, minimal residual disease (MRD) and disease relapse, highlighting an incomplete understanding of the mechanisms underlying these processes. In recent years, the impact of non-genetic factors on neoplastic transformations has increasingly been acknowledged, and growing evidence suggests that low oxygen (O2 ) levels (ie hypoxia) in the tumour microenvironment play a critical role in the development and treatment of cancer. As a result, there is a growing need to develop research tools capable of reproducing physiologically relevant O2 conditions encountered by cancer cells in their natural environments in order to gain in-depth insight into tumour cell metabolism and function. In this review, the authors highlight the importance of hypoxia in the pathogenesis of malignant diseases and provide an overview of novel engineering tools that have the potential to further drive this evolving, yet technically challenging, field of cancer research.

Oxygen-Based Nanocarriers to Modulate Tumor Hypoxia for Ameliorated Anti-Tumor Therapy: Fabrications, Properties, and Future Directions

Over the past five years, oxygen-based nanocarriers (NCs) to boost anti-tumor therapy attracted tremendous attention from basic research and clinical practice. Indeed, tumor hypoxia, caused by elevated proliferative activity and dysfunctional vasculature, is directly responsible for the less effectiveness or ineffective of many conventional therapeutic modalities. Undeniably, oxygen-generating NCs and oxygen-carrying NCs can increase oxygen concentration in the hypoxic area of tumors and have also been shown to have the ability to decrease the expression of drug efflux pumps (e.g., P-gp); to increase uptake by tumor cells; to facilitate the generation of cytotoxic reactive oxide species (ROS); and to evoke systematic anti-tumor immune responses. However, there are still many challenges and limitations that need to be further improved. In this review, we first discussed the mechanisms of tumor hypoxia and how it severely restricts the therapeutic efficacy of clinical treatments. Then an up-to-date account of recent progress in the fabrications of oxygen-generating NCs and oxygen-carrying NCs are systematically introduced. The improved physicochemical and surface properties of hypoxia alleviating NCs for increasing the targeting ability to hypoxic cells are also elaborated with special attention to the latest nano-technologies. Finally, the future directions of these NCs, especially towards clinical translation, are proposed. Therefore, we expect to provide some valued enlightenments and proposals in engineering more effective oxygen-based NCs in this promising field in this comprehensive overview.

Interfering with Tumor Hypoxia for Radiotherapy Optimization

Hypoxia in solid tumors is an important predictor of treatment resistance and poor clinical outcome. The significance of hypoxia in the development of resistance to radiotherapy has been recognized for decades and the search for hypoxia-targeting, radiosensitizing agents continues. This review summarizes the main hypoxia-related processes relevant for radiotherapy on the subcellular, cellular and tissue level and discusses the significance of hypoxia in radiation oncology, especially with regard to the current shift towards hypofractionated treatment regimens. Furthermore, we discuss the strategies to interfere with hypoxia for radiotherapy optimization, and we highlight novel insights into the molecular pathways involved in hypoxia that might be utilized to increase the efficacy of radiotherapy.

In Vivo Assessment of Hypoxia Levels in Pancreatic Tumors Using a Dual-Modality Ultrasound/Photoacoustic Imaging System

Noninvasive anatomical and functional imaging has become an essential tool to evaluate tissue oxygen saturation dynamics in preclinical or clinical studies of hypoxia. Our dual-wavelength technique for photoacoustic (PA) imaging based on the differential absorbance spectrum of oxyhemoglobin (oxy-Hb) and deoxyhemoglobin (deoxy-Hb) can quantify tissue oxygen saturation using the intrinsic contrast property. PA imaging of tissue oxygen saturation can be used to monitor tumor-related hypoxia, which is a particularly relevant functional parameter of the tumor microenvironment that has a strong influence on tumor aggressiveness. The simultaneous acquisition of anatomical and functional information using dual-modality ultrasound (US) and PA imaging technology enhances the preclinical applicability of the method. Here, the developed dual-modality US/PA system was used to measure relative tissue oxygenation using the dual-wavelength technique. Tissue oxygen saturation was quantified in a pancreatic tumor mouse model. The differences in tissue oxygenation were detected by comparing pancreatic samples from normal and tumor-bearing mice at various time points after implantation. The use of an in vivo pancreatic tumor model revealed changes in hypoxia at various stages of tumor growth. The US/PA imaging data positively correlated with the results of immunohistochemical staining for hypoxia. Thus, our dual-modality US/PA imaging system can be used to reliably assess and monitor hypoxia in pancreatic tumor mouse models. These findings enable the use of a combination of US and PA imaging to acquire anatomical and functional information on tumor growth and to evaluate treatment responses in longitudinal preclinical studies.

Metabolic Rewiring in Radiation Oncology Toward Improving the Therapeutic Ratio

To meet the anabolic demands of the proliferative potential of tumor cells, malignant cells tend to rewire their metabolic pathways. Although different types of malignant cells share this phenomenon, there is a large intracellular variability how these metabolic patterns are altered. Fortunately, differences in metabolic patterns between normal tissue and malignant cells can be exploited to increase the therapeutic ratio. Modulation of cellular metabolism to improve treatment outcome is an emerging field proposing a variety of promising strategies in primary tumor and metastatic lesion treatment. These strategies, capable of either sensitizing or protecting tissues, target either tumor or normal tissue and are often focused on modulating of tissue oxygenation, hypoxia-inducible factor (HIF) stabilization, glucose metabolism, mitochondrial function and the redox balance. Several compounds or therapies are still in under (pre-)clinical development, while others are already used in clinical practice. Here, we describe different strategies from bench to bedside to optimize the therapeutic ratio through modulation of the cellular metabolism. This review gives an overview of the current state on development and the mechanism of action of modulators affecting cellular metabolism with the aim to improve the radiotherapy response on tumors or to protect the normal tissue and therefore contribute to an improved therapeutic ratio.

Tumour Hypoxia-Mediated Immunosuppression: Mechanisms and Therapeutic Approaches to Improve Cancer Immunotherapy

The magnitude of the host immune response can be regulated by either stimulatory or inhibitory immune checkpoint molecules. Receptor-ligand binding between inhibitory molecules is often exploited by tumours to suppress anti-tumour immune responses. Immune checkpoint inhibitors that block these inhibitory interactions can relieve T-cells from negative regulation, and have yielded remarkable activity in the clinic. Despite this success, clinical data reveal that durable responses are limited to a minority of patients and malignancies, indicating the presence of underlying resistance mechanisms. Accumulating evidence suggests that tumour hypoxia, a pervasive feature of many solid cancers, is a critical phenomenon involved in suppressing the anti-tumour immune response generated by checkpoint inhibitors. In this review, we discuss the mechanisms associated with hypoxia-mediate immunosuppression and focus on modulating tumour hypoxia as an approach to improve immunotherapy responsiveness.

The Role of Tumor Microenvironment in Cancer Metastasis: Molecular Mechanisms and Therapeutic Opportunities

Simple Summary

Metastasis, the process by which cancer cells escape primary tumor site and colonize distant organs, is responsible for most cancer-related deaths. The tumor microenvironment (TME), comprises different cell types, including immune cells and cancer-associated fibroblasts, as well as structural elements, such as collagen and hyaluronan that constitute the extracellular matrix (ECM). Intratumoral interactions between the cellular and structural components of the TME regulate the aggressiveness, and dissemination of malignant cells and promote immune evasion. At the secondary site, the TME also facilitates escape from dormancy to enhance metastatic tumor outgrowth. Moreover, the ECM applies mechanical forces on tumors that contribute to hypoxia and cancer cell invasiveness whereas also hinders drug delivery and efficacy in both primary and metastatic sites. In this review, we summarize the latest developments regarding the role of the TME in cancer progression and discuss ongoing efforts to remodel the TME to stop metastasis in its tracks.

Abstract

The tumor microenvironment (TME) regulates essential tumor survival and promotion functions. Interactions between the cellular and structural components of the TME allow cancer cells to become invasive and disseminate from the primary site to distant locations, through a complex and multistep metastatic cascade. Tumor-associated M2-type macrophages have growth-promoting and immunosuppressive functions; mesenchymal cells mass produce exosomes that increase the migratory ability of cancer cells; cancer associated fibroblasts (CAFs) reorganize the surrounding matrix creating migration-guiding tracks for cancer cells. In addition, the tumor extracellular matrix (ECM) exerts determinant roles in disease progression and cancer cell migration and regulates therapeutic responses. The hypoxic conditions generated at the primary tumor force cancer cells to genetically and/or epigenetically adapt in order to survive and metastasize. In the circulation, cancer cells encounter platelets, immune cells, and cytokines in the blood microenvironment that facilitate their survival and transit. This review discusses the roles of different cellular and structural tumor components in regulating the metastatic process, targeting approaches using small molecule inhibitors, nanoparticles, manipulated exosomes, and miRNAs to inhibit tumor invasion as well as current and future strategies to remodel the TME and enhance treatment efficacy to block the detrimental process of metastasis.

Intratumor heterogeneity of breast cancer detected by epialleles shows association with hypoxic microenvironment

Rationale: In breast cancer, high intratumor DNA methylation heterogeneity can lead to drug-resistant, metastasis and poor prognosis of tumors, which increases the complexity of cancer diagnosis and treatment. However, most studies are limited to average DNA methylation level of individual CpGs and ignore heterogeneous DNA methylation patterns of cell subpopulations within the tumor. Thus, quantifying the variability in DNA methylation pattern in sequencing reads is valuable for understanding intratumor heterogeneity. Methods: We performed Reduced Representation Bisulfite Sequencing and RNA sequencing for tumor core and tumor periphery regions within one breast tumor. By developing a method named "epialleJS" based on Jensen-Shannon divergence, we detected the differential epialleles between tumor core and tumor periphery (CPDEs). We then explored the correlation between intratumor methylation heterogeneity and hypoxic microenvironment in TCGA breast cancer cohort. Results: More than 70% of CPDEs had higher epipolymorphism in tumor core than tumor periphery, and these CPDEs had lower methylation in tumor core. The CPDEs with lower methylation in tumor core may associate with hypoxic tumor microenvironment. Moreover, we identified a signature of five hypoxia-related DNA methylation markers which can predict the prognosis of breast cancer patients, including a CpG site cg15190451 in gene SLC16A5. Furthermore, immunohistochemical analysis confirmed that the expression of SLC16A5 was associated with clinicopathological characteristics and survival of breast cancer patients. Conclusions: The analysis of intratumor DNA methylation heterogeneity based on epialleles reveals that disordered methylation patterns in tumor core are associated with hypoxic microenvironment, which provides a framework for understanding biological heterogeneous behavior and guidance for developing effective treatment schemes for breast cancer patients.